Proteases are among the industrially most significant enzymes of all. In the context of washing and cleaning agents, proteases are the longest established enzymes that are contained in virtually all modern, high-performance washing and cleaning agents. They cause the breakdown of protein-containing stains on the item to be cleaned. Of these proteases, subtilisin-type proteases (subtilases, subtilopeptidases, EC 3.4.21.62) are particularly significant, which proteases are serine proteases owing to the catalytically active amino acids. Said proteases act as non-specific endopeptidases and hydrolyze any acid amide bonds that are within peptides or proteins. Their pH optimum is usually in the highly alkaline range. An overview of this family is found, for example, in the article “Subtilases: Subtilisin-like Proteases” by R. Siezen, pages 75-95 in “Subtilisin enzymes”, published by R. Bott and C. Betzel, New York, 1996. Subtilases are formed naturally by microorganisms. Of these, subtilisins that are formed by and secreted from Bacillus species should be mentioned in particular as the most significant group within the subtilases.
Examples of the subtilisin-type proteases that are preferably used in washing and cleaning agents are the subtilisins BPN′ and Carlsberg, protease PB92, subtilisins 147 and 309, protease from Bacillus lentus, in particular from Bacillus lentus DSM 5483, subtilisin DY, the enzymes thermitase, proteinase K and proteases TW3 and TW7, which belong to the subtilases but no longer to the subtilisins in the narrower sense, and variants of the mentioned proteases which have an altered amino-acid sequence by comparison with the starting protease. Proteases are altered, selectively or randomly, by methods known from the prior art, and are thereby optimized for use in washing and cleaning agents, for example. These methods include point, deletion or insertion mutagenesis, or fusion with other proteins or protein parts. Therefore, variants that are appropriately optimized are known for most of the proteases known from the prior art.
The European patent application EP 2 016 175 A1 discloses a protease from Bacillus pumilus provided for washing and cleaning agents, for example. In general, only selected proteases are at all suitable for use in liquid surfactant-containing preparations. In preparations of this kind, many proteases do not demonstrate sufficient catalytic performance or stability. In particular when used in washing agents which are usually purchased by the consumer in such an amount that several weeks or months may pass until the washing agent is finally consumed (i.e. the washing agents need to be stored by the consumer for weeks or months), many proteases demonstrate instability, which in turn leads to insufficient catalytic activity during the washing process. In phosphonate-containing liquid surfactant preparations, this problem is even more serious, for example due to the complex-forming properties of the phosphonates or due to disadvantageous interactions between the phosphonate and the protease.
As a result, protease- and surfactant-containing liquid formulations from the prior art have the disadvantage that, after storing, said formulations often do not have satisfactory proteolytic activity and therefore do not demonstrate optimal cleaning performance on protease-sensitive stains.